We plan to study influences affecting degeneration or regeneration of embryonic retinal ganglion cells in birds, and use of growth promoting substances to maintain ganglion cell viability and restore regenerative capacity of the cells. In addition, we plan to study preferential cell affinities, synapse formation, and other intercellular relationships between retinal or tectal cells or combinations of the two in long-term tissue cultures of dissociated embryonic avian retina.